Methods, apparatuses and systems for substrate processing for lowering contact resistance

ABSTRACT

Methods, apparatuses, and systems for substrate processing for lowering contact resistance in at least contact pads of a semiconductor device are provided herein. In some embodiments, a method of substrate processing for lowering contact resistance of contact pads includes: circulating a cooling fluid in at least one channel of a pedestal; and exposing a backside of the substrate located on the pedestal to a cooling gas to cool a substrate located on the pedestal to a temperature of less than 70 degrees Celsius. In some embodiments in accordance with the present principles, the method can further include distributing a hydrogen gas or hydrogen gas combination over the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application Ser. No. 62/665,114, filed May 1, 2018, which isincorporated herein by reference in its entirety.

FIELD

Embodiments of the present principles generally relate to substrateprocessing and more specifically to methods, apparatuses, and systemsfor substrate processing for lowering contact resistance.

BACKGROUND

Contact resistance, Rc, in semiconductor devices increases dramaticallywith reduction in scaling sizes. That is, smaller three-dimensionalstructures result in smaller contact areas, which result in rapidincreases in contact resistance. For example, with scaling, Al and Cupad openings are becoming smaller and smaller, making contactresistance, Rc, performance a challenge as high contact resistanceresults in loss of performance, errors in data and increased heat andpower loss, to name a few negative effects.

SUMMARY

Methods, apparatuses, and systems for substrate processing for loweringcontact resistance in at least contact pads of a semiconductor deviceare provided herein.

In some embodiments, a method of substrate processing for loweringcontact resistance of contact pads includes: circulating a cooling fluidin at least one channel of a pedestal; and exposing a backside of thesubstrate located on the pedestal to a cooling gas to cool a substratelocated on the pedestal to a temperature of less than 70 degreesCelsius.

In some embodiments in accordance with the present principles, themethod can further include distributing a hydrogen gas or hydrogen gascombination over the substrate.

In some embodiments, an apparatus for processing a substrate includes: aprocess chamber having a processing space contained therein; a processshield disposed within the process chamber and forming an upper andouter boundary of the processing space; and a pedestal disposed in theprocess chamber opposite the process shield and forming a lower boundaryof the processing space. In some embodiments, the pedestal comprises: anelectrostatic chuck assembly to enable chucking of a substrate on thepedestal; at least one first channel for carrying a cooling liquid alongthe pedestal to cool the substrate on the pedestal; and at least onesecond channel for carrying a cooling gas along the pedestal and endingin a respective hole in a top portion of the pedestal for exposing thecooling gas to a backside of the substrate.

In some embodiments, an apparatus for processing a substrate includes: aprocess chamber having a processing space contained therein; a processkit disposed in the process chamber to prevent undesired deposition onone or more components of the process chamber; a process shield disposedwithin the process chamber and forming an upper and outer boundary ofthe processing space; a gas diffuser to distribute a hydrogen processgas into the processing space and over the substrate; and a pedestal. Insome embodiments, the pedestal includes: an electrostatic chuck assemblycomprising an insulator material to enable high voltage chucking of thesubstrate on the pedestal; at least one first channel for carrying acooling liquid along the pedestal to cool the substrate on the pedestal;and at least one second channel for carrying a cooling gas along thepedestal and ending in a respective hole in a top portion of thepedestal for exposing the cooling gas to a backside of the substrate.

Other and further embodiments of the present principles are describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure, briefly summarized above anddiscussed in greater detail below, can be understood by reference to theillustrative embodiments of the disclosure depicted in the appendeddrawings. However, the appended drawings illustrate typical embodimentsof the disclosure and are therefore not to be considered limiting ofscope, for the disclosure may admit to other equally effectiveembodiments.

FIG. 1 depicts a high level block diagram of a process chamber inaccordance with an embodiment of the present principles.

FIG. 2 depicts a schematic cross-sectional view of a portion of theprocess chamber of FIG. 1 including the pedestal in accordance with anembodiment of the present principles.

FIG. 3 depicts a flow diagram of a method for cooling a pedestal and/ora substrate during substrate processing resulting in a reduced contactresistance in contact pads in accordance with an embodiment of thepresent principles.

FIG. 4 depicts a flow diagram of a method for pre-cleaning a processingenvironment previous to substrate processing resulting in a reducedcontact resistance in contact pads in accordance with an embodiment ofthe present principles.

FIG. 5 depicts a top view of a process kit having a reduction in anaccumulation rate of a polymer thickness build up in accordance with anembodiment of the present principles.

FIG. 6 depicts a cross-sectional side view of a process chamber inaccordance with at least some embodiments of the present disclosure.

FIG. 7 depicts a cross-sectional view of the gas diffuser in accordancewith at least some embodiments of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The figures are not drawn to scale and may be simplifiedfor clarity. Elements and features of one embodiment may be beneficiallyincorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

Embodiments of methods, apparatuses, and systems for substrateprocessing for lowering contact resistance in at least contact pads of asemiconductor are provided herein.

In various embodiments in accordance with the present principles, anelectrostatic chuck (ESC) assembly (also referred to herein as apedestal) includes a cooling system, for example at least one channelfor circulating a cooling liquid and a cooling means, such as a subzerochiller, for quickly cooling a substrate. In addition, in someembodiments in accordance with the present principles the ESC assemblyincludes at least channel for carrying a cooling gas and ending in atleast one hole for delivering a cooling gas to the backside of asubstrate to improve a cooling efficiency of the ESC. The inventorsdetermined that maintaining a substrate at lower temperatures (e.g.,below 70 degrees Celsius) during entire processing (e.g., an etchingprocess) results in lower contact resistance (e.g., as low as singledigit contact resistance measurements) of, for example, aluminum padopenings and copper pad openings in semiconductor devices.

Alternatively or in addition, in some embodiments in accordance with thepresent principles hydrogen gas or a hydrogen gas combination is addedto a process, such as a pre-clean process. For example, in someembodiments, hydrogen gas or hydrogen gas combination is added to aprocess gas, such as argon, of a process chamber for facilitating areactive removal of sputter polymers on surfaces (e.g., process kits) ofa process chamber and contaminants on contact pads.

For example, in one embodiment, adding hydrogen and/or a hydrogen/heliumgas combination to a process gas reduces the accumulation rate ofpolymer thickness build up on a portion of a process chamber, such as aprocess kit, which significantly increases the useful life of processkits, which are used to prevent undesired deposition on one or morecomponents of the process chamber. In addition, the cleaner processchamber environment reduces a risk of re-contamination of a substrateduring processing and thus results in lower contact resistance. Evenfurther, the addition of the hydrogen gas or hydrogen gas combination tothe process gas or to a substrate processing space of a process chamberafter the processing of the process gas, in accordance with alternateembodiments of the present principles, can reduce contaminants on padopenings/contact pads, such as Al or Cu pad openings and/or contactpads.

In various embodiments, to further facilitate cooling efficiencies in asystem in accordance with the present principles, an electrostatic chuck(ESC) assembly includes an insulator material which enables high voltagechucking without breakdown in the ESC. In addition, in some embodimentsin accordance with the present principles a process gas inlet is locatedat the top/center of a shield of a process kit to enable a process gasto directly flow into a process cavity to control gas flowrate/direction into the process cavity. That is, since some polymerbreak down is more sensitive to an amount of a hydrogen or hydrogencombination gas, enabling a process gas to flow directly into a processcavity enables a much more accurate control of a gas flow rate/directionof the process gas into the process cavity.

FIG. 1 depicts a high level block diagram of a process chamber 100 inaccordance with some embodiments of the present principles. The processchamber 100 of FIG. 1 comprises a housing 102 that surrounds a substrateprocessing region 104. The process chamber 100 of FIG. 1 furthercomprises a pedestal 110 having a substrate 111 thereon and a processshield 120. The process chamber 100 of FIG. 1 also illustrativelycomprises an optional gas diffuser 130. A pump 106 is coupled to theprocess chamber 100 to remove process byproducts and to facilitatemaintaining a predetermined pressure within the process chamber 100.

The pedestal 110 of FIG. 1 comprises an electrostatic chuck 112, whichin various embodiments comprises an optional insulator to enable highvoltage chucking (described in greater detail below). In addition, thepedestal 110 includes one or more RF power supplies, such as two RFpower supplies depicted in FIG. 1 (e.g., first RF power supply 114 andsecond RF power supply 116). The pedestal further includes a DC powersupply 118 coupled to the electrostatic chuck 112 for controlling theoperation thereof.

FIG. 2 depicts a schematic cross-sectional view of a portion of theprocess chamber 100 of FIG. 1 including the pedestal 110 and a coolingsystem 200 in accordance with an embodiment of the present principles.As depicted in FIG. 2, the pedestal 110 can include one or more deliverychannels or delivery portions 210 a, which can comprise deliveryportions of at least one fluid channel 210 of the cooling system 200.Similarly and as depicted in FIG. 2, the pedestal 110 can include one ormore delivery channels or delivery portions 250 a, which can comprisedelivery portions of at least one gas channel 250 of the cooling system200. The delivery portions 210 a, 250 a can provide a temperaturecontrolled fluid or a gas to the pedestal 110 for temperature control ofa substrate on which operations are being performed in the processchamber 100. The channels 210 can also include one or more returnportions 210 b that provide a return path for at least the temperaturecontrolled fluid from the pedestal 110.

FIG. 2 encompasses a variety of delivery and return configurations whichcan include a single or multiple channels that can distribute indifferent patterns within the pedestal 110, or can couple with multipleports in the pedestal 110. The embodiment of FIG. 2 is not to beconsidered limited to the single configuration illustrated, but canutilize any configuration that incorporates the components discussedherein. For example, a first fluid channel, such as a delivery channel,can provide fluid communication between a cooling apparatus 220 (e.g., achiller) and the pedestal 110, while a second fluid channel, such as areturn fluid channel, can provide fluid communication between thepedestal 110 and the cooling apparatus 220. For example in oneembodiment in accordance with the present principles, ethylene glycolcan be cooled using the cooling apparatus 220, such as a chiller, andcan be distributed within the pedestal 110 using the pedestal deliverychannel or delivery channels 210 a of the embodiment of FIG. 2, to coola substrate located on the pedestal 110.

In some embodiments in accordance with the present principles, a setpoint for the cooling of the cooling liquid, such as the ethyleneglycol, can be between −20 degrees Celsius and 0 degrees Celsius. Insome embodiments, a flow rate for the cooling liquid can be set atbetween 30-35 liters/min. For example, in some embodiments, the setpoint for the cooling of the cooling liquid can be between −20 degreesCelsius and 0 degrees Celsius and the flow rate for the cooling liquidcan be between 30-35 liters/min.

In accordance with various embodiments of the present principles, one ormore of the delivery portions 250 a (illustratively two of the deliveryportions) of the at least one gas channel 250 of the embodiment of FIG.2 can be used to distribute/communicate a cooling gas to a backside of asubstrate located on the pedestal. For example, in the embodiment ofFIG. 2, two of the delivery portions 250 a of the pedestal 110 terminatein respective (illustratively two) holes 235 on the top of the pedestal110. In various embodiments in accordance with the present principles,the delivery portions 250 a terminating in the holes 235 on the top ofthe pedestal can be used to deliver one or more inert gases, for exampleone or more noble gases, such as helium gas or a helium gas combination,to a backside of a substrate mounted on the pedestal 110 for cooling thesubstrate. For example, in some embodiments, pure helium gas can bedelivered from a gas supply 260 through the delivery portions 250 a ofthe pedestal 110 and through the holes 235 in the top of the pedestal110 to make contact with a backside of a substrate located on thepedestal 110 for cooling the substrate. In some embodiments, a heliumgas combination, such as a 5% H₂/He gas combination (e.g., about 5%hydrogen gas with the remainder helium), can be delivered from a gassupply 260 through the delivery portions 250 a of the pedestal 110 andthrough the holes 235 in the top of the pedestal 110 to make contactwith a backside of a substrate located on the pedestal 110 for coolingthe substrate.

In some embodiments, backside gas flow in accordance with the presentprinciples can be between 8 standard cubic centimeters/minute (sccm) to18 sccm and a minimal substrate backside pressure can be 4 Torr in orderto achieve good cooling.

Again, FIG. 2 encompasses a variety of delivery and returnconfigurations which can include a single or multiple channels that candistribute in different patterns within the pedestal 110, or can couplewith multiple ports in the pedestal 110. The embodiment of FIG. 2 is notto be considered limited to the single configuration illustrated, butcan utilize any configuration that incorporates the components discussedherein. In addition, although in the description of FIG. 2, a purehelium or helium gas combination is described, other pure gases or gascombinations, such as other inert or noble gases or gas combinations,can be used for cooling a substrate in accordance with the presentprinciples.

The backside cooling of a substrate in accordance with the presentprinciples, as described above, improves a cooling efficiency of aprocess chamber. More specifically, cooling a substrate as describedabove enables cooling a substrate from a typical 150 degrees Celsius (asis typical in process chambers during, for example, an etching process)to below 50 degrees Celsius in 10 seconds or less. Cooling a substrateas described above enables cooling of a substrate from temperatures ashigh as 300 degrees Celsius (or higher) to below 50 degrees.

The inventors have discovered that starting temperature for a substrateof 70 degrees Celsius or below advantageously helps minimize outgassingduring a chamber processing of a substrate and specifically during anetching step. In addition, the ability to rapidly cool down a substrate,in accordance with the present principles and as described above,minimizes a recipe time, which improves a system throughput whenprocessing substrates. The backside cooling of a substrate in accordancewith the present principles and as described above, enables maintaininga substrate at less than 70 degrees Celsius during an entire etchprocess.

In some embodiments in accordance with the present principles, theelectrostatic chuck 112 includes an insulator material to enable highvoltage chucking. The high voltage chucking in accordance with thepresent principles enables higher and more efficient transfer of thecooling from the pedestal 110 to a substrate on the pedestal 110 becausethe substrate is held more tightly against the cooled pedestal 110 dueto the high voltage chucking as compared to lower voltage chuckingpower. In some embodiments in accordance with the present principles, anoptimized combination of RF frequencies (e.g., 13.56 MHz and 60 MHzusing the first and second RF power supplies 114, 116) and powers allowsfor the best ratio of ions and radicals, and achieves an optimized waferbias for high voltage chucking.

In accordance with various embodiments of the present principles, aheating apparatus can be incorporated with or coupled with a deliveryfluid channel, and a temperature measurement device can be incorporatedwith or coupled with the return fluid channel to enable maintaining asubstrate mounted on the pedestal 110 at a specific temperature. A flowcontroller can also be incorporated with or coupled with the at leastone return fluid channel.

For example and as depicted in the embodiment of FIG. 2, a heater 215can be coupled with the delivery portion 210 a of the fluid channel. Theheater 215 can be any number of applicable heaters that are capable ofheating the temperature controlled fluid being delivered to the pedestal110. In one embodiment, the heater 215 can have a precision of betterthan +/−1 degree Celsius, and can have a precision of better than +/−0.5degrees Celsius, 0.3 degrees Celsius, 0.1 degrees Celsius, or better invarious embodiments. The heater 215 can also have a fast response timefrom the time a signal is received to adjust the temperature. Forexample, the heater 215 can have a response time per 1 degree Celsius ofless than or about 10 seconds from receipt of a communicationinstructing a change in temperature. The response time can also be lessthan or about 8 seconds, less than or about 5 seconds, less than orabout 4 seconds, less than or about 3 seconds, less than or about 2seconds, less than or about 1 seconds, less than or about 0.5 seconds,etc. or less.

The embodiment of FIG. 2 can also include a temperature measurementdevice 225 coupled with a return portion 210 b of the at least one fluidchannel 210. The temperature measurement device 225 can also becommunicatively coupled (e.g., as indicated by dashed line 227) with theheater 215 to provide temperature readings and adjustment informationfor controlling the temperature of the fluid delivered to the substratepedestal. In some embodiment, the temperature measurement device 225 canbe a thermocouple or resistance temperature detector, as well as anyother temperature sensing device. The temperature measurement device 225can be coupled with the return portion 210 b of the at least one fluiddelivery channel, and can be coupled with the return portion to directlycontact a fluid flowed through the at least one fluid channel, which canprovide more accurate temperature reading. The temperature measurementdevice can have an accuracy of higher than 1 degree Celsius, such asabout 0.1 degrees Celsius. The temperature reading can be delivered tothe heater 215, which can include additional hardware or software (notshown) to compare the return temperature of a temperature controlledfluid to a set point to determine whether temperature adjustmentutilizing heater 215 should occur.

The fluid utilized within the chamber portion depicted in FIG. 2 can beany known temperature controllable fluid, which can include water,steam, refrigerant, glycol, or any other fluid capable of temperatureadjustment. For example, many process operations require temperaturesbelow about 100 degrees Celsius, or below room temperature, if not downto sub-zero temperatures, and thus can include temperatures below orabout 80 degrees Celsius, 50 degrees Celsius, 40 degrees Celsius, 30degrees Celsius, 20 degrees Celsius, 10 degrees Celsius, 0 degreesCelsius, −10 degrees Celsius, etc. or less, including any range producedbetween any two of these temperatures. The foregoing temperature can bethe temperature of the substrate or the pedestal during any operation.For cooling operations, a temperature controlled fluid having a freezingpoint below the requisite temperature can be used, such as a refrigerantor a combination of water and glycol, such as ethylene glycol, in anyratio from about 0:1 to about 1:0, including a 1:1 ratio, for example.

As described above, the chamber portion of FIG. 2 can further include acooling apparatus 220 coupled with the delivery portion 210 a and returnportion 210 b of the at least one fluid channel 210. The coolingapparatus 220 can be located between the heater and temperaturemeasurement device within the loop, and can be on the same portion ofthe loop, or opposite portion of the loop as shown. The coolingapparatus 220 can comprise a chiller, heat exchanger, or any otherdevice capable of reducing the temperature of the temperature controlledfluid being flowed through the system. The cooling apparatus 220 can beoperated to singularly control the temperature of the temperaturecontrolled fluid in embodiments, and can also work in conjunction orcooperation with the heater 515 to achieve a precise deliverytemperature for the temperature controlled fluid.

The chamber portion depicted in FIG. 2 can further include a flowcontroller 230 coupled with a delivery or return portion of the at leastone fluid channel 210, such as in the return portion as illustrated inthe embodiment of FIG. 2. The flow controller 230 can include any numberof valves, pumps, orifice plates, or other devices used to regulateflow. The flow controller 230 can also be utilized in conjunction withthe heater 215 and the cooling apparatus 220 to regulate the temperatureof the pedestal 110 and a substrate mounted thereon. For example, a flowcan be increased or decreased to allow more or less temperaturecontrolled fluid to be delivered to the pedestal 110 based on heattransfer that can be occurring based on processing conditions. Althoughthe flow controller 230 may not have the accuracy or precision of theheater 215, for example, the flow controller 230 still can provide anadditional variable for adjustment during process operations to controlsubstrate and/or pedestal temperature.

In various embodiments in accordance with the present principles,hydrogen gas or a hydrogen gas combination is used in combination with aplasma sputter process to remove a polymer build-up from a surface of aprocess chamber and to remove contaminants from a contact pad. Forexample, in some substrate processing systems, a pre-clean step isimplemented to remove native oxide of metal contact pads prior to adeposition or etching process being performed on a substrate.Specifically, an argon sputter process is used to remove a surfacenative oxide layer from an aluminum pad and to remove organic materialcontamination form the aluminum pad surface. The inventors discoveredthat adding hydrogen gas or a hydrogen gas combination to a substrateprocess advantageously further assists in the removal of organicmaterial contamination from a contact pad surface and removal orreduction of a polymer build-up from a surface of the process chamber.

For example and referring back to the process chamber 100 of FIG. 1, insome embodiments in accordance with the present principles a gas source132 delivers hydrogen gas or a hydrogen gas combination (e.g., ahydrogen gas/helium gas combination) to the process chamber 100. The gassource 132 can also provide, alternatively or in combination, an inertgas, such as a noble gas, for example, helium gas. In the embodiment ofFIG. 1, the delivered hydrogen gas or hydrogen gas combination isreceived by the optional gas diffuser 130 and is distributed within theprocess chamber 100, for example through the process gas inlet 122located at the top/center of the process shield 120. In the embodimentof FIG. 1, the gas diffuser 130 is centrally located in a top of theprocess chamber 100 to enable a uniform distribution or flow of thehydrogen gas or hydrogen gas combination across a surface of thesubstrate 111 disposed on the pedestal 110. The gas diffuser 130 canalso control gas flow rate of a delivered hydrogen gas or hydrogen gascombination.

The inventors have discovered that adding hydrogen gas and/or a hydrogengas combination to a process gas advantageously reduces the accumulationrate of polymer thickness build up on a portion of the process chamber100 (e.g., a process kit of the process chamber, such as process shield120 or other process kit components such as described below), whichsignificantly increases the useful life of process kits and results in alower cost of consumables. For example, FIG. 5 depicts a top view of aprocess kit 500, for example, that can be disposed atop and about theperiphery of the pedestal 110. When hydrogen gas or a hydrogen gascombination is distributed over a surface of a substrate as describedabove, an accumulation rate of polymer thickness build up on a portionof the process kit 500 is reduced. In one illustrative embodiment, theinventors noted that when hydrogen gas is distributed over a surface ofa substrate during an Ar sputter process, an accumulation rate ofpolymer thickness build up on a lower wall portion 510 of the processkit 500 was significantly reduced as compared to an Ar sputter processalone. Distributing hydrogen gas or a hydrogen gas combination over asurface of a substrate within the process chamber 100 in accordance withthe present principles significantly increases the useful life ofprocess kits and results in a lower cost of consumables.

In alternate embodiments in accordance with the present principles, anAr sputter process is first performed and then a hydrogen gas orhydrogen gas combination is distributed over a surface of a substrate onthe pedestal 110 to remove organic material contamination form a contactpad surface and to reduce the accumulation rate of polymer thicknessbuild up on at least a portion of the process chamber 100. In variousembodiments in accordance with the present principles, a hydrogen gascombination can include a hydrogen/helium gas combination, such as a 5%H₂/He gas combination as described above.

The inventors also propose adding hydrogen gas or a hydrogen gascombination into the process gas or distributing a hydrogen gas or ahydrogen gas combination over the substrate after the process gas untila bonding energy for a bulk polymer surface is higher thanre-contaminated (Al—C) surface allowing selective removal of Al—Ccontaminant on Al pad to occur. The goal is to add an amount of hydrogengas or a hydrogen gas combination to enable removal of a contaminant ona contact pad while minimizing break down of bulk polymer.

In some embodiments to determine the effects of the distribution ofhydrogen gas or a hydrogen gas combination on at least one contact pad,a gas analyzer (not shown) can be implemented to detect, for example, anamount of polymer breakdown in a process. If the bulk polymer breakdownincreases with a higher flow of hydrogen gas or a hydrogen gascombination, the flow of hydrogen gas or a hydrogen gas combination canbe reduced to reduce an amount of bulk polymer breakdown and increase abreakdown of contaminants on a contact pad. Alternatively or inaddition, a gas analyzer can be used to monitor an amount of organicmaterial contamination being removed from the surface of a contact pad.If the organic material contamination being removed from the surface ofa contact pad increases with a higher flow of hydrogen gas or a hydrogengas combination, the flow of hydrogen gas or a hydrogen gas combinationcan be increased to further increase an amount of organic materialcontamination being removed from the surface of a contact pad.

Alternatively or in addition, in various embodiments in accordance withthe present principles, to determine the effects of the distribution ofhydrogen gas or a hydrogen gas combination on at least one contact pad,a contact resistance, Rc, of a contact pad can be measured. If thecontact resistance, Rc, increases with a higher flow of hydrogen gas ora hydrogen gas combination, the flow of hydrogen gas or a hydrogen gascombination can be reduced. Alternatively, if the contact resistance,Rc, decreases with a higher flow of hydrogen gas or a hydrogen gascombination, the flow of hydrogen gas or a hydrogen gas combination canbe increased. Thus, the flow of hydrogen gas or a hydrogen gascombination can be controlled, for example, until a maximum or desiredbenefit is detected.

In various embodiments in accordance with the present principles, toachieve an increased, and for example maximum, benefit from the additionof hydrogen gas or a hydrogen gas combination, the hydrogen gas orhydrogen gas combination is delivered to the process chamber 100 after asubstrate on the pedestal 110 of the process chamber 100 has been cooledby any of the processes described above. More specifically, hydrogen gasor a hydrogen gas combination is delivered to the process chamber 100after a substrate 111 on the pedestal 110 of the process chamber 100 hasbeen cooled as described above to ensure the right reactive selectivitywindow requirement is met.

Advantages of the processes described herein include longer process kitlife due to “self-cleaning” of process kits during process via H₂reactive removal of sputter polymers on kits and lower contactresistance, Rc, of conductive structures (for example, contact pads),due to the above described cooling processes and contamination removal.

Referring back to FIG. 1, in some embodiments in accordance with thepresent principles the process shield 120 includes a process gas inlet122 located at a top/center of the process shield 120, such that a gasor gas combination delivered to the process chamber 100 will flowdirectly into a process cavity of the process chamber 100. Because abreak-down of some polymer is more sensitive to hydrogen gas or ahydrogen gas combination than others, the delivery of a process gasdirectly to a process cavity enables a much more accurate control of aremoval or reduction of deposited polymers on surfaces of the processchamber or process kits associated with the process chamber inaccordance with the present principles and as described above.

FIG. 6 depicts a cross-sectional side view of a process chamber inaccordance with at least some embodiments of the present disclosure.More specifically, FIG. 6 depicts a process chamber and componentsthereof suitable for use as the process chamber 100 and the pedestal 110described above with respect to FIGS. 1 and 2. As depicted in FIG. 6,the process chamber 100 includes the pedestal 110 and the process shield120 disposed opposite the pedestal 110. In some embodiments, the processshield 120 can be coupled to or otherwise held against a lid 602 of theprocess chamber 100. Suitable gaskets, such as o-rings, can be providedbetween the lid 602 and the process shield 120 to prevent undesired gasflow or leakage between the lid 602 and the process shield 120. In someembodiments, one or more coolant channels 618 can be provided in the lid602 proximate to the process shield 120 to facilitate thermal control ofthe process shield 120.

The process shield 120 and pedestal 110 together define a processingspace therebetween. For example, the process shield 120 can define anupper and outer boundary of the processing space and a substrate supportsurface of the pedestal 110 can define a lower boundary of theprocessing space. The process shield 120 includes a curved inner surface604 opposite the pedestal 110. In some embodiments, the curved innersurface 604 is a continuously curved surface from a central portion ofthe inner surface 604 to an outer portion of the inner surface 604. Insome embodiments, the curved inner surface 604 continuously curvesradially outward and upward from a central portion of the inner surface604 to an outer portion of the inner surface 604 and then radiallyoutward and downward a portion of the inner surface 604 disposedradially outward of a substrate support surface of the pedestal 110 andthen radially outward and downward to a vertical or substantiallyvertical downwardly extending wall 606 of the process shield 120. Thedownwardly extending wall 606 terminates at a location below thesubstrate support surface of the pedestal 110 to create a flow path thatextends over the substrate support surface of the pedestal 110 anddownward along the outer periphery of the pedestal 110.

Gas is provided to the processing space through the process shield 120,for example, through a central opening in the process shield 120. Asdepicted in FIG. 6, gas diffuser 130, coupled to the gas source 132, isdisposed through the process shield 120 to provide a gas or gases asdescribed herein to the processing space. FIG. 7 depicts a more detailedcross-sectional view of a gas diffuser suitable for use as the gasdiffuser 130 in accordance with at least some embodiments of the presentdisclosure. As shown in FIG. 7, the gas diffuser 130 can be disposedwithin a central opening through the process shield 120. A centralopening is disposed through the lid 602 and to fluidly couple the gasdiffuser 130 to the gas source 132 (shown in FIG. 1 and FIG. 6).Suitable gaskets, such as o-rings or the like, can be provided tocontain gas flow from the gas source 132 through the lid 602 and the gasdiffuser 130 into the processing space of the process chamber 100.

In some embodiments, the gas diffuser 130 includes a cylindrical body706 having a radially outward extending flange 702 at a first end of thecylindrical body 706. The radially outward extending flange 702 mateswith a corresponding shelf formed in the process shield 120 and mayinclude openings to facilitate coupling, such as by bolting, the gasdiffuser 130 to the process shield 120. An opening 704 is formed throughthe first end and partially into the cylindrical body 706. Thecylindrical body 706 has a diameter at a second end, opposite the firstend and the flange 702, that is less than a diameter of an openingformed through the process shield 120 to form an annular gap 710 betweenthe outer sidewall of the cylindrical body 706 and the sidewall of theopening in the process shield 120. A plurality of openings 708 areformed through the sidewall of the cylindrical body 706 between theopening 704 and the outer sidewall of the cylindrical body 706 tofluidly couple the gas source 132 and the processing space through thegas diffuser 130, as indicated by arrows 712. In some embodiments, theplurality of openings 708 include a plurality of radial openings, suchas cylindrical holes, formed through the cylindrical body 706.

Returning to FIG. 6, the gas flow exiting the processing space isdirected to plenum 608 disposed to the side of and radially outward ofthe pedestal 110. The plenum 608 can be an annular plenum, for exampleincluding an inner portion 614 comprising an annular wall, an upperradially outward extending flange, and a lower radially outwardextending flange. An outer portion 616 extends between the upperradially outward extending flange, and a lower radially outwardextending flange to enclose the plenum 608. A plurality of openings 610are provided in the annular wall of the inner portion 614 to allow gasfrom the processing space to enter the plenum 608. Although FIG. 6discloses one configuration of components to form the plenum 608, otherconfigurations can also be used to exhaust the process gases from theprocessing space along the side of, and below, the substrate supportsurface of the pedestal 110. The plenum is coupled to the pump 106.

FIG. 3 depicts a flow diagram of a method 300 for cooling a pedestaland/or a substrate during substrate processing resulting in a reducedcontact resistance in accordance with at least some embodiments of thepresent principles. The method 300 may be performed in the apparatusdisclosed herein. The method 300 begins at 302 during which a coolingfluid is circulated in at least one channel of a pedestal to cool asubstrate on the pedestal. As described above, in some embodiments inaccordance with the present principles, a cooling fluid, such asethylene glycol, can be cooled using a cooling apparatus 220. Thecooling fluid is circulated in channels 210 of the pedestal 110 to coolthe pedestal 110. The cooling fluid flow rate and temperature may becontrolled as described above to cool the pedestal and/or substrate to adesired temperature. The cooled pedestal 110 is then able to cool asubstrate located on the pedestal 110.

At 304, a backside of a substrate located on the pedestal 110 is exposedto a cooling gas. As described above, in some embodiments in accordancewith the present principles, at least one channel in the pedestal 110carries helium gas or a helium gas combination to at least one hole 235in the pedestal 110 for exposing the backside of the substrate to thehelium gas or the helium gas combination. The cooling gas, e.g., heliumgas or a helium gas combination, can be controlled as described above tofacilitate cooling the substrate to a desired temperature.

In some embodiments, the method 300 can be performed subsequent to asubstrate process having a substrate temperature above room temperature.For example, in some embodiments, the method 300 can be performedsubsequent to a degas process where the substrate is at a temperature ofabove 150 degrees Celsius. In some embodiments, the method 300 can beused to cool a substrate from a temperature at or above 150 degreesCelsius to a temperature of at or lower than 70 degrees Celsius, forexample at or lower than 50 degrees Celsius. In some embodiments, themethod 300 can cool the substrate to the aforementioned temperature in10 seconds or less.

FIG. 4 depicts a flow diagram of a method 400 for pre-cleaning aprocessing environment previous to substrate processing resulting in areduced contact resistance in accordance with an embodiment of thepresent principles. The method 400 may be performed in the apparatusdisclosed herein. The method 400 begins at 402 during which a substrateprocessing region is cooled. As described above, in some embodiments inaccordance with the present principles, a pedestal and/or a substrate iscooled, for example, as described above with respect to the method 300.Such cooling of the pedestal/substrate results in a cooling of thesubstrate processing region.

At 404, hydrogen gas or hydrogen gas combination is distributed over asubstrate in the substrate processing region. As described above, in oneembodiment in accordance with the present principles, hydrogen gas orH₂/He combination is delivered to a substrate processing region alongwith an argon process gas. The addition of hydrogen gas or H₂/Hecombination to a process gas, either before, during, or after, forexample a pre-clean process, reduces an accumulation rate of a polymerthickness build up on a portion of a process chamber, such as a processkit, which significantly increases the useful life of process kits andreduces a risk of re-contamination of a substrate during processing. Theaddition of hydrogen gas to a process gas, either before, during, orafter, for example a pre-clean process, also reduces a contamination ona surface of a contact pad as described above.

In some embodiments, a sputter etch process can be performed to cleanexposed surfaces of a conductive feature (e.g., a contact pad) on thesubstrate, for example using an argon sputter etch process as describedabove. For example, before, during, or after 404 is performed, a sputteretch process can be performed, such as an argon sputter etch process, toclean the exposed surfaces of the conductive feature (e.g., the contactpad). Such cleaning can include removal of oxides, such as AlOx fromaluminum contact pads (or other oxides from contact pads of othermaterials such as, for example, copper). The removal of the native oxidecan be performed before, during, or after 404, in which organiccontamination (such as Al—C) is removed from the conductive feature.

In one specific exemplary embodiment, a substrate 111 having exposedcontact pads surrounded by polymer dielectric material can be firstsubjected to a degas process. The degas process can have an elevatedtemperature of, for example, 150 degrees Celsius or more. The substrate111 can subsequently be cooled as described with respect to the method300 above to reduce the substrate temperature from at or near the degastemperature to less than 70 degrees Celsius, or less than 50 degreesCelsius within about 10 seconds or less. Next, a hydrogen gas or H₂/Hecombination is provided to the process chamber 100 and distributed overthe substrate 111 in the substrate processing region as described abovewith respect to the method 400. A sputter etch pre-clean process, suchas an argon sputter etch process, can be performed as described above toremove contaminants, such as a native oxide, from the exposed contactpads. In some embodiments, the hydrogen gas or H₂/He combination can beprovided prior to performing the sputter etch pre-clean process. In someembodiments, the hydrogen gas or H₂/He combination can be provided whileperforming the sputter etch pre-clean process. In some embodiments, thehydrogen gas or H₂/He combination can be provided subsequent toperforming the sputter etch pre-clean process.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof.

1. A method of substrate processing for lowering contact resistance ofcontact pads, comprising: circulating a cooling fluid in at least onechannel of a pedestal; and exposing a backside of the substrate locatedon the pedestal to a cooling gas to cool a substrate located on thepedestal to a temperature of less than 70 degrees Celsius.
 2. The methodof claim 1, further comprising: flowing a hydrogen gas over thesubstrate.
 3. The method of claim 2, wherein the hydrogen gas comprisesa hydrogen gas combination.
 4. The method of claim 2, wherein thehydrogen gas is flowed during a pre-clean process.
 5. The method ofclaim 2, wherein the hydrogen gas is flowed after a pre-clean process.6. The method of claim 2, wherein the hydrogen gas is flowed incombination with argon gas.
 7. The method of claim 1, wherein thecooling gas comprises helium gas.
 8. The method of claim 1, wherein thecooling gas comprises a hydrogen/helium gas combination.
 9. The methodof claim 1, further comprising chucking the substrate to the pedestalusing an electrostatic chuck.
 10. An apparatus for processing asubstrate, comprising; a process chamber having a processing spacecontained therein; a process shield disposed within the process chamberand forming an upper and outer boundary of the processing space; and apedestal disposed in the process chamber opposite the process shield andforming a lower boundary of the processing space, wherein the pedestalcomprises: an electrostatic chuck assembly to enable chucking of asubstrate on the pedestal; at least one first channel for carrying acooling liquid along the pedestal to cool the substrate on the pedestal;and at least one second channel for carrying a cooling gas along thepedestal and ending in a respective hole in a top portion of thepedestal for exposing the cooling gas to a backside of the substrate.11. The apparatus of claim 10, wherein the process shield includes acurved inner surface opposite a support surface of the pedestal.
 12. Theapparatus of claim 11, wherein the curved inner surface curves radiallyoutward and upward from a central portion of the inner surface to anouter portion of the inner surface and then radially outward anddownward a portion of the inner surface disposed radially outward of asubstrate support surface of the pedestal and then radially outward anddownward to a substantially vertical downwardly extending wall of theprocess shield.
 13. The apparatus of claim 11, wherein the processshield further includes a substantially vertical downwardly extendingwall that terminates at a location radially outward of and lower than asubstrate support surface of the pedestal.
 14. The apparatus of claim10, further comprising a cooling device configured to cool the coolingliquid to a temperature of less than 70 degrees Celsius.
 15. Theapparatus of claim 10, further comprising a gas diffuser coupled to theprocessing space to flow a gas over the substrate.
 16. The apparatus ofclaim 15, wherein the gas diffuser is disposed in a central opening ofthe process shield.
 17. The apparatus of claim 16, wherein the gasdiffuser has a cylindrical body having a diameter smaller than adiameter of the central opening to define an annular gap between thecylindrical body and the process shield, and wherein the cylindricalbody further includes a plurality of radial openings through a sidewallof the cylindrical body to fluidly couple the annular gap to an openingformed in the cylindrical body.
 18. The apparatus of claim 15, furthercomprising a gas source coupled to the gas diffuser, wherein the gassource provides hydrogen gas or a hydrogen/helium gas combination aloneor in combination with an inert gas.
 19. The apparatus of claim 10,wherein the cooling gas comprises at least one of a helium gas or ahydrogen/helium gas combination.
 20. Apparatus for processing asubstrate, comprising; a process chamber having a processing spacecontained therein; a process kit disposed in the process chamber toprevent undesired deposition on one or more components of the processchamber; a process shield disposed within the process chamber andforming an upper and outer boundary of the processing space; a gasdiffuser to distribute a hydrogen process gas into the processing spaceand over the substrate; and a pedestal, comprising: an electrostaticchuck assembly comprising an insulator material to enable high voltagechucking of the substrate on the pedestal; at least one first channelfor carrying a cooling liquid along the pedestal to cool the substrateon the pedestal; and at least one second channel for carrying a coolinggas along the pedestal and ending in a respective hole in a top portionof the pedestal for exposing the cooling gas to a backside of thesubstrate.